Musical instrument



J. A. KOEHL 2,562,670

MUSICAL INSTRUMENT 5 Sheets-Sheet l I E i LAM I QJQ . 3&1?

July 31, 195] Filed April 22, 1949 July 31, 1951 J. A. KOEHL MUSICAL INSTRUMENT 5 Sheets-Sheet 2 Filed April 22, 1949 frzd'erzfar Q. 4.1M-

July 31, 195] J. A. KOEHL MUSICAL INSTRUMENT 5 Sheets-Sheet 3 Filed April 22, 1949 J. A. KOEHL MUSICAL INSTRUMENT July 31, 1951 5 Sheets-Sheet 4 Filed April 22, 1949 July 31, 1951 J. A. KOEHL MUSICAL INSTRUMENT 5 Sheets-Sheet Filed April 22, 1949 Jkz/erz far.

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Patented July 31 1951 MUSICAL INSTRUMENT James A. Koehl, Evanston assignments, to Central Inc, Chicago, 111., a corporation of Delaware Application April 22, 1949, Serial Nb. 89,123

16 Claims.

This invention relates to musical instruments and broadly to a readily portable organization of elements for electrically producing organ and orchestral tones from the playing-keys of any conventional keyboard.

The invention relates more specifically to an attachment for keyboard musical instruments such as pianos, pipe, reed and electric organs or other keyboard musical instrumentsfor the production of sustained musical tones of any selected timbre from the instruments keyboard, which said tones can be played singly or in en'' semble with tones produced by mechanism typical oisaid instrument.

The invention is also directed to certain improvements in the invention disclosed and broadly claimed in my prior Patent No. 2,250,085 of July 22, 1941. The invention disclosed in said patent embodies electric switches which are coactive with respective playing-keys" of a piano or other keyboard musical instrument for selective activa tion of electronic devices with resultant produc'-' tion of organ-like tones. In a broader sense and as distinguished from the device disclosed in said patent, the herein disclosed invention mayor may not be used with any inexpensiveand readily por table keyboard which not necessarily a art of a musical instrument and is'used' solely in combination with theco'ntiol mechanism for producing musical tones from said keyboard.

The herein disclosed invention is essentially characterized by structural features enabling" quick and convenient attachment thereof to any conventional keyboard or to the keyboard of a piano, pipe, reed or electric organ or any other keyboard instrument without any necessity for making structural changes in the case or console of the instrument,. and in like manner, removed therefrom and readily carried from one place to another as and when desired.

Further objects and advantages of the invention, are:

(a) The provisionof a device which can be at'- tached to any conventional keyboard for pro-' ducing sustainedtones in response to playing'any selected playing-keys of said keyboard.

(b) The provision of a device adapted to be supported upon the case or console of any keyboardmusical instrument and correctly related to the keyboard and maintained in fixed relation to the keyboard to prevent accidental derangement thereof;

(c) The provision of a compact attachment, the control mechanisms of which are readily accessible to the player.

, 111., assignor, by mesne Commercial Industries,

(d) The provision of a device, which, when combined with another keyboard musical instru-'- ment will enable tones produced thereby to be mixed and played with tones produced by the instruments customary sound producing mecha-' nism.

(e) The provision of a device which, when attached to many makes of pipe, reed and electric organs will provide same with additional voices and thereby greatly increase the musical poss'i-' bilities and advantages thereof.

(f) The provision of an inexpensive, light weight and readily portable device of attractive appearance.

Other objects and advantages will appear'froin' the following description and upon reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a suitable electric circuit which may be employed in carry ing the invention intop'ractice;

Figure 2 is a view similar to Figure l of a fur ther form of useful circuit;

Figure 3 is a front view of a piano showing the device attached thereto;

Figure 4 is a view partly in section and partly in elevation of aportion of a piano and a por tion of the attachment, illustrating in detail the means for enabling both longitudinal and vertical adjustment of the switch assembly and for securing the assembly to the case of the piano;

Figure 5 is a section taken approximately on line 55 of Figure 3;

Figure 6 is a view in elevation of one of the electric switches, showing same in an off position;

Figure 7 is a view similar to Figure 5, showing" the switch in an on position;

Figure 8 is a view in front elevation of an organ showing the invention attached thereto;

Figure 9 is a view partly in section and partly in elevation showing in detail the means for adjustably mounting the key assembly over the keyboard of the organ shown in Figure 7';

Figure 10 is a perspective view of the cable attaching means employed in the embodimentshown at Figure 3;

Figure 11 is a vertical section through a portable structure embodying. a conventional keyboard showing my key assembly applied thereto The herein disclosed invention may employ, in combination with electric switches, most anywell known formof electronic mechanism for producing sustained musical tones of any selectedtimbre. Reference is made to theinven'tion dis-- closed in United-States Letters Patent to Larsen,.

herein disclosed embodiment of my invention,

there will be twelve sets of oscillators in which the oscillators are connected in cascade and the frequencies of said oscillators controlled so that there would be a set of oscillators for all C notes, a set for all Cit notes, a set for all D notes, etc. to and inclusive of a set producing octavely related frequencies for all B notes. These generators are connected in circuit with respective elec- I tric switches, a wave filter system and an electroaco ustical system for the'conversion of selected tone frequencies into audible sounds of any selected timbre. Y

As the primarypurpose of the present invention isthe provision of 'a simple and inexpensive organization of elements adapted'for use in combination with most any keyboard instrument, it is necessary that the mechanisms comprising same shall fulfill their purpose in a highly dependable manner and that the device shall be applicable to a great number of keyboard instruments in general use.'

At Figure 1 is shown in block diagram twelve sets of vacuum tube oscillators lettered C, C#, D, 1 34?, E, F, Fit, G, Git, A, A# and B. Each separate set of said oscillators has its oscillators connected in cascade which may be accomplished either in the manner set forth in said Larsen et allpatent, No. 2,410,883 or by any other well known circuit in which a first oscillator operating at a given frequency is coupled in cascade with a plurality of slave oscillators, the respective oscillators of each cascade'providing octavely related complex waveforms. When my invention is used in combinatioh'with a piano it will ordinarily provide sixty complex tone frequencies respectively corresponding to the vibration frequencies of notes C2--B5 of the keyboard of the piano. However, this may be departed from and in some instances, oscillators producing wave forms at the tone frequencies of all the eighty-' eight notes of the piano will be provided. It suffices to say thatat Figure 1 each cascade of oscillators provides fiveoutput leads I.

At said Figure l is shown an assembly of playing-key actuated electric switches. In practice, there will be one of these switches for each-playing-key of the pianokeybo'ard producing tones at said vibration frequencies C2-B5. To avoid complicating the circuit only a few of the total number of said switches are shown. Only twelve of-them are connected to respective frequency sources, namely, switches respectively coactive with playing-keys associated with notes C3-B3. As each separate cascade produces only five complex octavely related frequencies, then, and assuming that the first stage produces the highest frequency, we canassume'that the lead I in the middle of the five leads running from each separate cascade is from the .third oscillator of said cascade, such that the middle lead I from cascade C furnishes switch C3 with an audio signal corresponding to the vibration frequency of note- C#3, and so on to and inclusive of the middle output lead I from cascade B which furnishes an audio signal to switch B3.

Each of the aforementioned key actuated switches comprises a movable contactor '2 connected with a respective lead 5, a fixed contactor 3 connected to ground 4 and a fixed contactor 5 connected to a common output conductor 6. When the playing-keys are-elevated their coac tive movable switch contactors 2 engage the fixed contacts 3 and the oscillators are grounded. When any key is depressed, the movable contactor moves into engagement with its coactive fixed contact 5 and the signal flow is from a respective oscillator to said common conductor 6. Wave filters l havetheir input sides connected to said common conductor and, as shown, the output side of each filter'is provided with an electric switch 8, which, when close circuited, as desired, causes the output wave from said filter to be impressed on a conductors connected withthe input cirwit o a a d freq en ra i if i 62 the. output circuit of which is a loud speaker l i." said amplifier is equipped with a volume control dc; vice 12. It follows that as the'output wave froin' any oscillator of the cascaded setso'f'cscillators is rich in harmonics, these waves will be repeated in the outputs of said wave filters as waves, 'cer-' tain of the upper harmonics of'whi'ch' have been suppressed. A filter system capable of functioning in this manner is disclosed'in the aforementioned Larsen Patent No.2 ,403,090. When a cir-' cuit functioning as aforesjtated is used in conibination with a pipe, reed or any well known electric organ, the wave form in'theoutp'ut of any filter can be convertedinto' audible sound at any 7 desired amplitude and canbeplayd in ensemble with tones of any selected timbre produced by, the frequency or vibration producing means of said organ. Tones produced either bythe'organ wave filters, the complex output'waves from the oscillators can be converted into substantially sinusoidal waves or waves less "complex than those produced by said oscillators; In this man-' nor, an organ, thetones or voices of which are wholly reedy can, bythe method and means herein employed be provided with simple and de=-' pendable sources from which'a great variety of orchestral and organ-like tones'are available as desired. By this method," inexpensive organs now' in use and having only a very limited number of voices can be brought toa high standardof development and by a simple and inexpensive organization of elements 'capableofapplication to most any organ in a 'minimu'm'of time. Even" expensive organs canbe mate'riallyimprove-d by addition thereto of the herein'disclosed invention. Particularly is-this true in those instances where an organ lacks certain solo voices, which, if added to an organ would necessitate costly installation of many pipes and/or reeds and other bulky space consumin accessories.

An alternative form of circuit is" shown at Figure 2. In this embodiment of my invention, the output conductors Sa from the keying switches (not shown) are connectedto the input power amplifier ,,(I iOt,shown) via, circuit leads -l 6. Acircuit of this character is also; disclosed irrsaid Larsen Patent No. 2,403,090, 111 many respects.

aseaet'o this circuit :is superior ltO the circuit shown at Figure :1 :in that the :nutputwaves from different bus-bars [4 can be brought together through branch resistive paths I] such that the wave from :one bus-bar. can be of a different amplitude than the wave taken .off of another one of said bus-bars. For the better installations; this method, while more costly than the method shown at Figure 1, enables producing at a given stop I 5,-a wave whichis the sum of two or more waves fromdifferent filters.

, Referring now to the form of my invention shown at Figure 3, the attachment comprisesa rectilinear housing I8 embodying a lower section 1.9 and an upwardly extending medial section 20. Said housing can be of any appropriate length depending upon the total number .of tone sources employed and the number of electric switches intended to be connected in circuit therewith. The piano P may be of any conventionalmake and, as shown at Figures 3 and 4, the housing is vertically disposed and lies at the extreme back ends of the effective playing-surfaces of the playing-keys of the instruments keyboard, the thickness of the housing or dimensions from front to back being approximately one-half inch so as not to interfere with motion of the fingers over the playing-keys. The end portions of the housing have projecting therefrom horizontally disposed threaded rods 2 I each provided with an internally threaded longitudinally adjustable sleeve 2| (1, the outer end of which terminates in a flat felt faced clamping disk 22. Mounted to turn freely on each rod is a metallic member 23 which is provided with a vertically adjustable foot 24 whose lower .face is felted as at 25. On each rod 2| is a nut 26. When attaching the housing to the piano, it is placed vertically at the rear of the playing-keys and when an operative relation of the housing to the playing-keys is established, the sleeves 2la are turned so as to advance the disks 22 firmly against the inner surfaces of the side pieces B of the case of the piano. The foot pieces 24 are brought to rest on the upper surfaces of the cheeks C of said case and are secured in fixed positions of vertical adiustment by clamp nuts 21. Clamp nuts 2b on rods 21 are then firmly adjusted against the inner ends of sleeves 21a. The structural features just described permit both longitudinal and vertical adjustment of the switch housing, the purpose for which will be manifest as the description proceeds.

At Figures 5, 6 and 7 are shown the electric switches 28 of the assembly of switches which are coactive with'respective playing-keys of'the piano keyboard, and the stop switches which are contained in the medial portion of the housing. In each case, the switches are arranged in longitudinal rows. I

The playing-key actuated switches may be of the form and construction disclosed'in the patent to Larsen et al. No. 2,484,977, November 15, 1949. These switches each essentially consist of a pin 30 mounted in portion 19 of the housing for free sliding motion vertically and provided with "a downwardly projecting portion 3| which extends sumciently below the bottom of the housing to enable its lower end to rest on the playing surface of a respective playing-key, so that by the normal upward tension of spring 32 on the playing-key, both the key and the pin are urged upwardly, the pin to an off position of the switch and the key to a fully elevated position. Inwardly of the housing section IS, the pin 30 is threaded at 33 for "coaction witha traveling nut 34 of hard insulating material. .35 and 36 are respective bus-bars, and, as shown, a coil spring 3 of suitable light gauge silver "wire has its lower portion electrically connected to a clip 31a. to which an output terminal I from a respective tone frequency source is'adaptedto be connected. Bus-bar .35 is grounded at 38 and when .pin .30 is elevated, aredu'ced portion 39 ofcoil spring 31 engages same. The spring, by reason of its at tachment to said clip and to nut 34 tends .normally to urge the pin in a downward direction, thereby enabling. the pin to follow the playingkeyras the latter is being depressed, such that when the key is lowered the small upper exten sion 59 leaves the bus-bar .35 and engages buss bar 36. The pins 3.0., of which there are sixty in the described embodiment of my invention, are spaced apart longitudinally a distance enabling each separate pin to make .free contact with arespective playing-key as shown at .Figure 3.

The stop switches ofwhich .only one is shown at Figure 5, comprises a .free vertically sliding pin 40 provided with alug 4| of hard insulating material. The pin .is slidable in an insulating block 42 situated in the portion 20 of the housing. .Its lower end is rounded at 43 and rests freely on the cam 44a of a stop tab 44. Coactive with the pin is a coil spring 45, the lower end of which is soldered to a terminal clip 46 secured to a fixed block 4] of hard insulating material. The reduced upper coil 48 of spring 45 is secured to lug 4| and has its free extremity projecting between a grounded bus-bar 49 and an output bus-bar 50, the former of which has engagement with said reduced upper portion 48 of the spring. In this position of the parts, tab 44 is in its raised, position. The inner end of the tab has the extremity of its cam 44a pivoted at 5i to an extension 52 of block 41. Block 47 .has a fiat leaf spring 53, the free end of which iscoactive with the angular faces 54 and 55 of said cam 44a so as to hold the tab in any position of angular adjustment.

When the stop switch is off tab 44 occupies the position shown at Figure 5. Pin 40 has moved upwardly where the portion 48 of the contact spring engages the grounded bus-bar 49. Spring 53 retains the tab in this position. Current flow is from clip 46, through the spring 45 and to ground through bus-bar 49. When the tab is depressed, the pin 40 follows the motion thereof and rides said cam 44a, thus compelling portion 48 of the spring to approach and electrically contact bus-bar 50. Motion in this direction is limited by engagement of lug 4! with astop 58 on block 42. The switch is then in an on condition. The current now is then from terminal 46, through spring 45 and to the power amplifier via bus-bar 50.

All lead wires to and from the playing-key switches and the stop switches areformed into a cable which is strung in the lower portion of the aforementioned switch housing. The free end of the cable extends from one end of the housing and preferably through a cable attaching tubing 51. This tubing has a long leg 58 which rests on the adjacent cheek of the case of the piano, a depending portion 59 which lies in front of the piano, and a short rearwardly extending leg 60 which underlies the bed plank and is secured thereto by a strap 5|.

The expression control device 62 (Figure 3) is preferably situated to the left of the vertical center line of the switch housing and secured tothe bed plank so asito be. readily actuable by the knee of the player At. Figures 8 and9, the invention is shown applied to an organ. For the purpose of the in vention the-organ may be. one in which tones are .produced either by. pipes, reeds or by any well known electrical system employing frequency generators forproducing wave forms that are adapted to beconverted .into audible sounds for musical expression. One such system is disclosed in the aforementioned Larsen patent; No. 2,403,090. Another form to. which. the invention is applicable is disclosed in the Hammond patent, .No. 1,956,350. In Figure 8, the attachmentwhich is identified by the same reference numerals assused inthe first described embodiment of. the invention is mounted over the keyboard 63 of theorgan 0. In .this case, the invention' employs a slightly different type of switch housing and mounting means. -In the form ofthe invention-first described, thesame is-used with an instrument having88 playingkeys. The normal note compass of anorganis five octaves. For this-reason, though it willnot follow in all instances, the switch housing is substantially coextensive with the keyboard. Its ends are mounted in vertical guide waves '64 formed in blocks 65 so as to be adjustable vertically. Switch housing 18 is provided with adjusting screws 66 movable throughfixed plates 61 and provided with knobs 68., By turnin the knobs in the plate 61 andby swiveling the lower ends of the screws 66 to the-housing, the latter can be raised and lowered as desired and the contact pins of the switches operatively related to their respective keys. When a necessary adjustment has been made, jamb nuts 09 on the screws are advancedagainst the plates 6.! so as to hold them againstretrograde. Blocks may be-securedto the inner faces of the. side pieces OI of theconsole ofthe organ, their lowerends terminatingat the upper surfaces of the cus v tomary cheeks 70. The block 65 at the right. of Figure9 is hollowed out as at H, the hollow portions communicatingwith one end of the switch housing and, as illustrated, the upper end of this hollow portion is open as at 12. This enables the cable 13 from the various switches to be concealed, except at the point where itis passed over an adjacent side OI of the console. In this embodiment of the invention, the por-. tion of the housing which extends upwardly. and accommodates the stop switches and control tabs is disposed to theright of the stop tabs 02 of the organ. This isa detail that is provided for the sake of convenience and accessibility of all stop tabs to the player. In some types of organs, the position occupied 'by the stop tabs of the attachment will be different. Also in this em: bodiment of the invention, the volume control device 74 preferably includes a pedal 15 disposed in close proximity 'tothe expression pedal 03 of the organ. When using an organ embodying my attachment, voices obtainable either by the attachment or by the organ can be played separately or together as-desired. When mixing an electronically produced'tone with a tone produced by pipes or reeds, there is an advantagenot heretofore possible with other organs, namely, that there can be mixed with the tone producedby the organ a tone produced by the attachment in which most any shading in the amplitude thereof can be controlled, There are many instances when playing anorgan that only a negli sib ermeu tqi atone oi one m r i r ssed to be mixed with a tone of; anothertimbrei in order to give a more or less correct mixture. .This' can be .accomplished with unusual nicety. by the means employed herein. Istress particularly an attachment fonr'nost any type" oforgan which can be used-in conjunction with the keyboard and will contribute to the organ innumerable devices that heretofore would-have been costly to install in either a pipe or reed organ. I further-stress that feature of the invention which enables the device to be attached readily and is portable, inexpensive and: when attachedwillnot in any manner interfere with the normal play ing of an organ. While I have shown a single manual, the invention is in no manner limited in this respect. Similar attachments can be ap plied to as many manuals asdesired: In each case, the individual attachments would have individual volume control devices. Among other novel features, I particularly stress the feature which comprises a switch as sembly that can be quickly attached to and removed from a keyboard and when attached and the switch actuating pins of-the switches correctly coordinated with the'respective playingkeys, the assembly will be capable of resistingany manual force that may beapplied thereto in any direction when the keyboard is played or when force, either in a downward or an up warddirection is applied as can result when manipulating the stop tabs 44. In theabsence of means for preventing derangement of the switch assembly, tilting of the assembly from an intended horizontal position could result inan accidental close circuiting or partial close'circui ting of the playing-key-actuated switches with the result that output tone signals from the various oscillators'will be effectivein thenet work such that unwanted sounds would be heard at the loud speaker H. I have shown and described an assembly of key operated electrical switches disposed above the keyboard 'of an organ. This is because of the great number of organs in use and not that there is an intention to limit the invention in this respect. Pipe organs have certain acknowl-' edged advantages' over electric organs. "Electric organs have certain acknowledged advantages over pipe organs, such for examplatheir ability faithfully to produce many orchestral tones by relatively inexpensive methods, devices and mech-J anisms that require only a minimum'of space for their accommodation. Except for the swell boxes of a pipe organ, all tones speak at the same intensity and it, is impossible to reduce the sound level with that nicety that is characteristic of electronic instruments in which the volume of produced sound can be reducedalmost to'ja whisperj Thus, it follows that any pipeor reed. organ can be greatly improved by additionthereof of the herein described improyements. V

The playing-key supporting springs, one of. which is shown, at Figure 5, are'such thatthe resiliency thereof is sufficiently in excess of that of the springs'o'f the keying switches as to effec-. tively lift the pins when pressure is removed from the keys, thereby restoring the switches to open circuited conditions in exact time with manipulation of the keys. 'f At Figure 11, a portable structure consists of means such as a case having a conventional keyboard 8 I. The case has its ends 82-82 formed with vertical slots 83-- 83. The key switch and mixer assembly 34 are the same as the forrn shq aai hea se, assert tha enewal-redsproject from the opposite ends of the assembly housing and are accommodated in the respective slots 83-83 for vertical adjusting and are provided with clamp nuts 85 adapted to be brought into clamping engagement with the outer faces of said ends 82-422 to secure the housing in a position of vertical adjustment where the playing-key actuated pins 86 will be operatively related to the respective playing-key of the keyboard. V

What I claim as my invention is:

1. An attachment for keyboard musical instruments of the class employing a case and means actuable by each separate playing-key of the keyboard of said instrument for producing a musical tone having the vibration frequency of argivennote of a musical scale, said attachment comprising an assembly of longitudinally spaced apart electric switches disposed for actuation by respective playing-keys of said keyboard in response to application of playing pressure to and removal of same from said keys, means for detachably mounting said switch assembly on said case for adjustment to vertically aline different switchesof said assembly with respective ones of said keys and for securing said assembly in a position of fixed adjustment, each of saidswitches including an actuator which is vertically adjustable relative to the playing-surface of a respective playing-key and means responsive to actuation of said switches when playing said keys for producing musical tones having the vibration frequencies of notes associatedwith said keys.

2. An attachment as set' forth in claim 1 wherein ,said mounting means; comprises devices on saidswitch assembly engageable with portions of said case at the respective ends of said keyboard.

3. An attachment as set forth in claim 1, wherein said mounting means comprises devices carried by said switch assembly at the respective ends thereof for clamping engagement with portions of said case at the respective ends of said keyboard.

4. An attachment as set forth in claim 1, wherein the switch assembly includes a longitudinal housing disposed above said keyboard at the back ends of the playing-keys and wherein the mounting means includes devices at the re spective ends of said housing, for engagement with portions of said case at the respective ends of said keyboard.

5. An attachment as set forth in claim 1, wherein said mounting means includes extensible devices carried by said switch assembly at the respective ends thereof for fastening said assembly to said case at the respective ends of said keyboard.

6. An attachment as set forth in claim 1, wherein means are provided for coaction with said switch assembly and said case for positively preventing vertical movement of said assembly when said assembly has been adjusted to establish the aforementioned relation of said switches to said respective playing-keys.

7. An attachment as set forth in claim 1, wherein said mounting means is provided with means engageable with said case for preventing vertical movement of said switch assembly when said assembly has been adjusted to establish the aforementioned relation of said switches to said respective playing-keys.

8. An attachment as set forth in claim 1, wherein said mounting means comprises longitudinally extensible devices at the opposite ends '10 of said switch assembly for clamping engagement with adjacent portions of said case.

9. An attachment as set forth in claim 1, wherein an enclosure is provided for said switch assembly and includes an upper extension containing a selectively actuable, hand operated mixer with stop control devices disposed in front of the extension, and wherein means are provided for coaction with said case to resist force in a downward direction when actuating said stops and prevent downward movement of the switch assembly from an established position of adjustment thereof.

10. The combination with a piano and means for electrically generating audio signals at the tone frequencies of notes associated with given playing-keys of the keyboard of said piano and for translating said signals into audible sounds for musical expression; n electric switch assembly removably connected with the piano at the respective ends of and disposed above said keyboard at the back ends of the playing-keys thereof, and embodying longitudinally spaced apart electric switches associated with and actuable by assigned ones of said playing-keys, and electrically connected to said signal generating means for translation of signals into audible sounds when depressing selected ones of said playing-keys, means enabling adjustment of the assembly respectively in longitudinal and vertical planes, and means for securing said assembly in a position of selected adjustment.

11. The combination with a horizontally dis-- posed keyboard, each playing-key of which has pivotal motion about a horizontal axis, and means for electrically generating audio tone signals having the vibration frequencies of different notes of a musical scale with which different playing-keys of said keyboard are associated, of an organization of electric switches connectedin circuit with said signal generating means, each separate switch of said organization of switches having an actuator which is yieldingly urged axially in a direction to lightly press against a respective key of said keyboard to follow pivotal motion of the key and thereby cause operation of the switch, and means for vertically aligning the actuators of given switches of said organization of switches with preassigned playing-keys of said keyboard and selectively adjusting the actuators vertically.

12. The combination with a horizontally disposed keyboard, each playing-key of which has pivotal motion about a horizontal axis, and means for electrically generating audio tone signals having the vibration frequencies of different notes of a musical scale with which different playing-keys of said keyboard are associated, of an organization of electric switches connected in circuit with said signal generating means, each separate switch of said organization of switches having an actuator which is yieldingly urged axially in a direction to lightly press against a respective key of said keyboard to follow pivotal motion of the key and thereby cause operation of the switch. and means coactive with said keyboard at the respective ends thereof for vertically aligning the actuators of given switches of said organization of switches with preassigned playing-keys thereof and adjusting the actuators vertically.

13. In mechanism of the class described, the combination with means embodying a horizontally disposed keyboard, each playing-key of which has pivotal motion about a horizontal axis, and means for electrically generating tone signals having the vibration frequencies of notes of a musical scale with which different playing-keys of said keyboard are associated; of an organization of electric switches connected in circuit with said signal generating means, each separate switch of said organization of switches having an actuator which is yieldingly urged axially in a direction to lightly press against a respective key of said keyboard to follow pivotal motion of the key and thereby cause operation of the switch, means enabling adjustment of the switches as a unit relative to said keyboard, and means enabling individual adjustment of the actuator of any one of the aforementioned switches relative to a respective playing-key.

14. In mechanism of the class described, the combination with means embodying a horizontally disposed keyboard, each playing-key of which has pivotal motion about a horizontal axis, and means for electrically generating tone signals having thevibration frequencies of notes of a musical scale with which different playing-keys of said keyboard are associated; of a horizontally disposed rigid bar mounted for vertical and longitudinal adjustment relative to said keyboard and provided with playing-key actuated electric switches connected in circuit with said signal generating means and arranged in a longitudinal row above and at the back ends of the efiective playing surfaces of said playing-keys and spaced apart from each other so that different ones of said switches are disposed for actuation by respective ones of said playing-keys, a system of electrical stop control devices carried by said bar and connected in circuit with said signal generating means, and means for securing said bar in fixed relation to said keyboard.

15. In mechanism of the class described, the combination with a case having a horizontally disposed keyboard; of means for electrically generating tone signals having the vibration frequencies of notes of a musical scale with which diflerent ones of said keys are associated and for translating said signals into audible sounds, a

horizontally disposed rigid bar provided with playing-key actuated electric switches connected in circuit with said signal generating means and arranged in a longitudinal row above and at the back ends of the efiective playing surfaces of said playing-keys and spaced apart from each other so that different ones of said switches are disposed for actuation by respective ones of said playing-keys, said bar being applicable as a unit to said case and being adjustable horizontally and vertically to establish and maintain a coactive relation of each separate switch to a respective playing-key.

16. In a musical instrument employing a case and a keyboard supported in a playing position by said case, means actuable from said keyboard for producing sustained musical tones in the pitch relation to notes of a musical scale with which respective playing-keys of said keyboard are associated, said means including a set of electric switches in which individual switches thereof are disposed for activation by said respective playingkeys; and a cable composed of tone signal input and output wires connected with said respective switches, said cables being substantially wholly concealed by structural parts of the case, except for a free end which extends externally thereof, as and for the purpose set forth.

JAMES A. KOEHL,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

